Diode-pumped visible wavelength alkali laser

Abstract

In the basic Diode-Pumped Alkali Laser (DPAL) device, excitation to the n .sup.2P.sub.3 / 2 electronic level by a single diode laser pump source leads to a population inversion between the first excited electronic .sup.2P.sub.1 / 2 level and the ground .sup.2S.sub.1 / 2 level, permitting the construction of efficient, high-power, compact DPAL laser oscillators in the near infrared spectral region. The present invention extends the single-step excitation DPAL to a two-step excitation, or up-conversion DPAL to produce efficient, powerful laser operation in the visible blue and near UV spectral regions (viz., in the range 460-323 nm). The present invention describes an apparatus and method that efficiently sums the energy of two, near-infrared diode pump photons in alkali vapor atoms, followed by stimulated emission to their electronic ground levels.

Description

[0001] This is a continuation-in-part of U.S. patent application Ser. No. 10 / 000,508, titled "Diode-Pumped Alkali Laser" filed Oct. 23, 2001 and incorporated herein by reference.BACKGROUND OF THE INVENTION[0002] 1. Field of the Invention[0003] The present invention relates to visible and near ultraviolet wavelength lasers, and more specifically to diode-pumped up-conversion alkali lasers (DPALs).[0004] 2. Description of Related Art[0005] With the coming of the Internet and the explosive growth in data communications it enabled, there has been a concomitant growth in the demand for ever-more capable visual displays in the form of electronic cinema, home theater, desktop, and mobile displays. The growth in data generation and communications has also created an accelerating demand for high density data storage, taking many physical forms including optical data storage in video DVD disks, and in optically written holograms in polymer coated disks. Advanced realizations of high-performan...

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Benefits of technology

[0020] The use of an alkali atomic vapor element as laser active specie in a near infrared Diode-Pumped Alkali Laser (DPAL) has been disclosed [10] in U.S. Patent Application Serial No. 10 / 000,508, titled "Diode-Pumped Alkali Laser" filed Oct. 23, 2001, and incorporated herein by reference. In the basic DPAL device, excitation to the n .sup.2P.sub.3 / 2 electronic level by a single diode laser pump source leads to a population inversion between the first excited electronic .sup.2P.sub.1 / 2 level and the ground .sup.2S.sub.1 / 2 level, permitting the construction of efficient, high-power, compact DPAL laser oscillators in the near infrared spectral region. The present invention extends the single-step excitation DPAL to a two-step excitation, or up-conversion DPAL to produce efficient, powerful laser operation in the visible blue and near UV spectral regions (viz., in the range 460-323 nm). The present invention describes an apparatus and method that efficiently sums the energy of two, near-infrared diode pump photons in alkali vapor atoms, followed by stimulated emission to their electronic ground levels.

Problems solved by technology

The arc lamp is generally limited in brightness because its output light is radiated into all spatial directions, is inefficient in producing useful visible light, produces a great amount of waste heat, and has an awkwardly short lifetime usually measured in 100's of hours.

These laser sources have working efficiencies of 2-5 percent, produce output powers up to the watt range, but have proven to be many times too expensive for wide-spread use in consumer display applications.

This phenomenon spoils the phase-matching condition for efficient harmonic generation and greatly limits the operating lifetime of the device, especially at the higher output levels [4].

This problem has proven to be most difficult in generating shorter visible wavelengths (e.g., s blue).

Also the precision required to fabricate micron scale diode stripe lasers and couple them efficiently into narrow width single-mode waveguides is a challenging and relatively expensive task to perform.

Thus, the market demand for relatively lower-cost, compact, efficient, high-power (0.1 to 10 watts), and long-lived (>>20,000 hours) visible (especially blue) laser sources continues unfulfilled.

While technically adequate, the current manufacturing methods of such diodes is a low-yield process, owing to the lack of a suitably lattice-matched substrate upon which to epitaxially grow these laser diode devices [8].

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